This invention relates, in general, to a system and method for establishing a communication connection and is particularly, but not exclusively, applicable to network architectures that support differing resource capabilities and which combine narrowband call control, services and routing with broadband connectivity.
Globally, telecommunication systems are, generally, in a transitional phase between first generation, narrowband digital networks (such as the Global System for Mobile (GSM) cellular communication system) and future, multi-media digital networks (such as the Universal Mobile Telecommunication System (UMTS)) having broadband capabilities. This transition is necessarily required to support higher data rate communications, including video and internet applications, that are presently being both considered and made available. Unfortunately, this transitional phase also presents system operators with several dilemmas, and also prejudices immediate implementation of such broadband systems. For example, until such a time when a free-standing broadband system becomes an accepted and freely available standard for all subscriber terminals (such as cellular telephones and data transmission devices), system operators are reticent to write-off their significant investments in current narrowband infrastructure technology. Indeed, such narrowband infrastructure technology already provides a rich set of services and service creation environments which would have to be re-implemented to be deployed in broadband networks. Consequently, present-day narrowband systems must be adapted to accommodate both narrowband and broadband users; with this statement particularly relevant to call establishment and interworking procedures between these different forms of network.
For an effective migration between narrowband and broadband systems (for the transitional phase), system operators must particularly consider an interworking scenario when all subscribers connect to a. narrowband network, but one or more intermediate broadband networks are used to relay information between these narrowband subscribers.
In more detail, telecommunication networks comprise nodes connected by communication resources (usually termed xe2x80x9clinksxe2x80x9d), with a particular network technology characterised by the means of transmission of user and control information along these links and also by the routing and relaying functions embodied in the nodes. The term routing is used to describe the process of determining the path the information will take through the network, while relaying is the process of transferring information from one link to another, i.e. the information is merely passed, without alteration, from one channel resource to another.
Taking GSM as an exemplary form of a narrowband digital network, user and control information (or xe2x80x9cdataxe2x80x9d) is interleaved, using time division multiplexing (TDM), on a 52 kbit per second (kbps) pulse code modulated (PCM) bearer channel. Indeed, these bearer channels can each framed to support four voice calls of 16 kbps, comprised from 13 kbps of sampled and encoded speech and 3 kbit/s of ancillary information, such as parity check and correction bits (and the like) and synchronisation information. Data is then relayed across a node by some form of synchronous TDM switching fabric, often of the xe2x80x98time-space-timexe2x80x99 type. Control information (e.g. call set up and tear down messages) logically follows the same path (although not always the same physical path) through the network as user information, and is terminated in each node for routing purposes. Routing is conventionally performed, in each node, on a xe2x80x98hop-by-hopxe2x80x99 basis using long lived routing tables, i.e. the node is sufficiently intelligent to determine an optimum route for the succeeding network connection.
Control information is regulated by a signalling scheme that is distinctive to the type of network employed. Particularly, public signalling systems are used between nodes of a public network and between public networks of different operators. Signalling System No. 7 is the only important example of a public signalling system. Access signalling systems are used between subscribers and edge nodes of public networks, e.g. between a radiotelephone and a base station subsystem (BSS). In fact, the most common digital access signalling schemes are Common Channel Signalling Systems, such as the Integrated Service Digital Network (ISDN) DSSS1 signalling schemes (and its predecessors) and Channel Associated Signalling schemes that are both derived from analog signalling. Private schemes are generally derived from access schemes but provide richer functionality within personal networks, such as within a secure private branch exchange (PBX).
On the other hand, broadband digital networks are characterised in that user and control information is transmitted in fixed or variable length xe2x80x98packetsxe2x80x99, with these packets prepended with headers that contain bearer channel identification. In contrast with narrowband systems, user information is relayed across a node via an asynchronous switching fabric that examines each packet in turn (using some kind of fairness algorithm) and directs it to the appropriate output link in response to the input link and bearer channel identification. Routing and control information transmission is, however, similar to that for the narrowband case, and differs only inasmuch as the signalling schemes are technology specific.
To facilitate use of broadband networks and the migration of communication networks to high data rate technologies (e.g. the 2 Mbps rate envisaged within UMTS), there is a need to provide an effective mechanism for interconnecting narrowband networks through a transparent broadband ether. In other words, the broadband ether must accommodate and support narrowband signalling schemes without affecting either data integrity or in any way inhibiting data flow or interconnection.
According to a first aspect of the present invention there is provided a method of establishing a communication connection across a broadband network from a first terminal in a first narrowband network to a second terminal in a different narrowband network, the broadband network having a signalling protocol dissimilar to those provided in the respective first and second narrowband networks, the method comprising the steps of: at the first narrowband network and on a first communication circuit, receiving an incoming call request from the first terminal, the incoming call request containing an address of the first terminal and a destination address associated with the second terminal; selecting a phantom trunk different to the first communication circuit, the phantom trunk having a circuit identity and being arranged to support a narrowband communication between the first narrowband network and the second narrowband network; in a first message, sending the destination address and the circuit identity from the first narrowband network to the second narrowband network; in a second message, sending the circuit identity and the address of the first terminal to the second narrowband network; identifying the presence of the circuit identity in both the first message and the second message to establish that the communication connection is between the first terminal and the second terminal; and establishing the communication connection through the broadband network.
In a second aspect of the present invention there is provided a communication system having a broadband network and a plurality of narrowband networks each containing at least one communication device, the narrowband networks having differing signalling protocols to those of the broadband network and wherein the narrowband networks are interconnected through the broadband network, the communication system arranged to establish a communication connection between a calling communication device in a first narrowband network and a receiving communication device in a different narrowband network, each of the at least one communication devices having an address, each of the plurality of narrowband networks comprising: a call server responsive to a call request message generated by the calling communication device, the call request message containing the address of the calling communication device and a destination address associated with the receiving communication device, the call server being arranged to identify a circuit identity associated with a first communication circuit used to send the call request message to the call server; means for selecting a phantom trunk different to the first communication circuit, the phantom trunk having a circuit identity and being arranged to support a narrowband communication between the first narrowband network and the different narrowband network; means for sending, in a first message, the destination address and the circuit identity from the first narrowband network to the second narrowband network; means for sending, in a second message, the circuit identity and the address of the calling communication device to the second narrowband network; means for identifying the presence of the circuit identity in both the first message and the second message to establish that the communication connection is between the calling communication device and receiving communication device; and means for establishing the communication connection through the broadband network.
In another aspect of the present invention there is provided a connection broker arranged to orchestrate interconnection of a first narrowband communication unit of a first narrowband network to a second narrowband communication unit of a different narrowband network via a broadband network, the broadband network having dissimilar signalling protocols to those provided in the respective first and different narrowband networks, the first narrowband communication unit and the second narrowband communication unit each having an address, the connection broker coupled to a call server that is responsive to a call request message generated by the first narrowband communication unit, the call request message containing the address of the first narrowband communication unit and a destination address associated with the second narrowband communication unit, the call server being arranged to identify a circuit identity associated with a first communication circuit used to send the call request message to the call server and having means for selecting a phantom trunk different to the first communication circuit, the phantom trunk having a circuit identity and being arranged to maintain a narrowband communication between the first narrowband network and the different narrowband network, the call server further including means for sending, in a first message, the destination address and the circuit identity from the first narrowband network to the second narrowband network, the connection broker comprising: means for sending, in a second message, the circuit identity and the address of the first narrowband communication unit to the second narrowband network; and a processor, responsive to the receipt of the first message and the second message, for identifying the presence of the circuit identity in both the first message and the second message to establish that the communication connection is between the first narrowband communication unit and the second narrowband communication unit.
Advantageously, the present invention allows the interconnection of different narrowband networks through a broadband network notwithstanding that no common signalling protocols exist between the narrowband and broadband networks.